In general, in plate-making and printing operations, before the regular printing called a running-on has been done, a proof printing is done so as to examine a printing plate obtained by a plate-making operation and to obtain a standard printed material for a running-on operation.
Since the proof printing is done for the purpose of examining a standard printed material for a running-on operation, it is desirable that the proof printing be done under the conditions close to those for the running-on. Namely it is preferable that the proof printing be done by using a printing machine for running-on. However, the construction of a printing machine for running-on is not convenient for carrying out an operation for printing a small quantity of materials, such as a proof printing operation. Due to the necessity of operating a printing machine efficiently, the proof printing is done by a proof printing machine, i.e. a proofing press, such as a flat-bed planographic press.
In general, in a flat-bed press, such as a proof press, printing is one by moving a carriage, which includes an ink roller, a dampening roller and a blanket, on a press body frame provided with a plate bed, a paper bed, a dampening unit disposed at one end of the frame, and a swingable roller (rider roller) disposed at the other end of the frame for use in applying ink to an inking unit or an ink roller.
In a proof printing operation or a running-on operation for printing a small quantity of materials, which is carried out by a conventional flat-bed press, such as a proof press, an operator feeds materials to be printed, such as paper piece by piece by hand onto a paper bed, and push the materials, which are thus fed, lightly by the tips of his fingers so as to drive the materials to a front guide or a side guide, i.e., the feeding of the materials is done physically.
When one lot of materials to be printed consists of around 10-20 pieces of paper, they may be fed manually by an operator without much trouble. However, when the number of pieces of paper to be printed is large, it becomes very difficult to feed the paper with a high efficiency in a short period of time.
In a printing operation by a conventional, flat-bed press, such as a proof press, grippers holding the printed material on a paper bed are opened by an operator's foot pedal stepping operation, and the printed material is then taken up by hand. When the operator then removes his foot from the foot pedal, the grippers are closed to complete the paper discharging operation. This operation temporarily stops the printing process and cause a loss of time.
In a conventional printing machine, the printed material are thus taken out one by one by hand from the paper bed, i.e., by an inefficient method.
When one lot of printed materials consist of around 10-20 pieces of paper, they may be discharged manually by an operator without much trouble. However, when the number of pieces of printed paper is large, it becomes very difficult to discharge the printed paper with a high efficiency in a short period of time.
In a flat-bed press, such as a proof press, the monochromatic printing is generally done. In order to carry out a multicolor printing operation by using this printing machine, the printing is done initially in a first color, and the operation of the printing machine is then stopped, the printing machine being then washed. A printing operation using a second color is thereafter started. As many operations as the number of required colors are repeated to obtain multicolor printed materials.
Therefore, carrying out a multicolor printing operation by a flat-bed press, such as a proof press requires considerable time and labor, and multicolor printed materials cannot be obtained by speedy and simple operations in practice.
It is known that some people have attempted to carry out a multicolor printing operation by using a flat bed press without stopping the machine in the midst of the operation. For example, the printing machine disclosed in Japanese Patent Laid-Open No. 134209/1976 is adapted to carry out a multicolor printing operation by using inking units and plate beds the numbers of which correspond to that of the required colors. Although the multicolor printing may certainly be done by this printing machine, a considerable number of constituent parts of the printing machine are divided into as many groups as the number of the required colors. Therefore, the construction of the printing machine is liable to become complicated. Moreover, when the size of the materials to be printed is large, a printing machine of extremely large dimensions is required. Accordingly, this printing machine may be used suitably for the materials to be printed of a comparatively small area but it is not for the materials to be printed of a large area.
The greater part of the operations including an ink supplying operation in a flat-bed press, such as a proof press is carried out manually. For example, the ink is applied to an ink roller and some other rollers by a manual operation as the ink applied thereto is leveled manually to a uniform thickness. Namely, the supplying of ink, the replenishing of ink and the regulating of the thickness of the layer of ink on the rollers, and so on are done by spreading ink over the rollers by a spatula. This means that the controlling of the feed rate of the ink supplied to the ink roller is done relying upon nothing but the experience of the operator. Therefore, a great deal of skill is required to obtain printed materials of quality stable in terms of the quantity of ink in use, and the operational error readily occurs before the materials are printed with a predetermined quantity of ink. This causes the operation efficiency to lower.
A proof press provided with an inking unit is also known. This inking unit is similar to the inking unit in a printing machine for running-on. Consequently, if an inking unit is installed in a conventional proof press, it is necessary to buy a high-priced inking unit.
An ink supply unit which can be used in a proof press is also known. For example, a device for supplying ink via an ink supply nozzle to an ink duct or an ink roller is known.
There are many flat-bed presses in which the feeding and discharging of materials to be printed are generally done by hand. When a considerable number of materials are printed by such a printing machine, these manual operations are not easy to carry out but they require a great deal of labor. The registering of paper, a material to be printed, during the feeding thereof is also done through a manual operation.
It is, in view of the above points, an object of the present invention to provide a comparatively simple device for carrying out the feeding or, in addition to this, discharging of materials to be printed in a flat-bed press, such as a flat-bed planographic machine utilized generally as a proof press, and thereby solve the above-mentioned problems.
It is another object of the present invention to provide a flat-bed press, such as a flat-bed planographic machine utilized generally as a proof press, or a flat-bed printing method, which is capable of carrying out a multicolor printing operation and obtaining printed materials of a stable quality through an automated printing operation, and which enables even an unskilled operator to obtain printed materials of a stable and uniform quality.
It is still another object of the present invention to provide a flat-bed press or a flat-bed printing method, which is capable of making multicolor printed materials at a higher speed as compared with a conventional flat-bed press.